Shipbucket

Keep in mind that in that case there's not going to be much of a point in having a secondary battery beyond hitting torpedo boats or possibly destroyers. You might want to reduce the size of your medium battery then.

Hmm... I really kicked myself in the groin there.

EDIT: Everything in this post except the first line is edited in later. I was tired at the momment of this post, but felt I should answer it. I'm filling in my thinking/reasoning here.
First of, I'm loath to do anything to the caliber of the secondary artillery. It was one of the two distinguishing features that this design was built around in my head.
The ROF differance of a 152mm and a 170mm gun isn't that big. The weight of the shell, on the other hand, is entirely different. About 45-50kg against 65-70kg(increase weight about +30%), earned on only 18mm(increase caliber about 11%) and a ROF (assumably) marginaly lower.
To further support this comparation, I'm also mentioning the datas of the Bofors designs of 152mm M/12 and the 283mm M12. 45-ish kg against a 305kg shell, both guns with an almost equall ROF. According to navweaps both could shoot about 3-4 RPM. Other sources state that the ROF of the 152mm was 5-6(find this more plausible). With this one can assume the differance between 152mm and 170mm would be... third of a shot less per minute? quarter? Quintel*?
One can assume the range would differ to some degree as well.
Don't belive I didn't consider changing the caliber though. But with these figures, I'm not convinced that it would pay of using a smaller gun.
*Is "quintel" a word? Meh, is now.